The present
article describes a (hopefully less confusing) subset of
technological choices to be recommended for implementation.

The Train

The conventional
train has traditionally consisted of a locomotive pulling some
unpowered wagons, but modern passenger trains tend to have the
locomotive functions (electric motors) integrated in the passenger
wagons. This is like a laptop computer: elegant and convenient when
everything works well, but awkward when a problematic part needs to
be replaced. A wagon or train full of passengers is ill suited for
motor replacement.

The beamway train
can and should be designed to combine the advantages of both
approaches.

The
elements making up a small beamway train/tram/bus.(Shapes are not
shown in this diagrammatical representation.)

A beamway train
should have one or two wagons. An elevator should be in the end of
the first wagon, or constitute a separate "wagon" employed
between the two real wagons. The wagons hang under a series of
"microlocs" – small locomotives handling both the
suspension and propulsion. These have traditionally consisted of
motorized bogies running inside a hollow beam, but we will mainly use
air cushions for holding up the train, and then it will be more
appropriate to speak about sleds instead of bogies.

From each sled
goes a suspension connection (controlling the height and providing a
soft suspension) down to the wagon. The wagon only needs to have the
small motors which displace the suspension sideways.

Microlocs might be
programmed or remotely controlled for running alone, but will
normally work in teams, and usually for carrying a train as depicted
above. Alternatively, a team of something like 3-10 microlocs may be
connected to a very thin "wagon" which is hardly more than
a beam. When this is connected to an end of a train – perhaps
the nearest suspension – we have something like a conventional
locomotive. Such a miniloc, used before and/or after a train or
wagon, can be useful for giving a train some extra pulling power.

Beamways may run
on different kinds of beams: The hollow and flat types will be
described below. These will require different kinds of microlocs, but
the lower part of the microlocs – the suspension rods and their
connection to the wagon top – should be standardized, so that
the same wagons may be used with different beam types.

Wheels?

Wheels
are inefficient for carrying the weight of a train at high speed. The
contact between train and track becomes brutal and energy wasting at
high speeds. Inflated rubber wheels give a softer ride, but they are
unreliable. Sliding along without mechanical contact can be done at
high speeds using magnetic fields (maglev)
or air
cushions. As air cushion hovering can be used with a plain track
– without special equipment like electromagnets or coils
mounted all the way along the track – it is preferred in this
recommendation. But even if wheels are not used for carrying the
weight, they are useful for propulsion. Propulsion power can be
delivered efficiently from electric hub motors, and positioning the
train can be done reliably in hills and strong winds when wheels are
used.

When high traction
is needed – for acceleration at low speeds, or for
hill-climbing – propulsion may have to deliver a force
corresponding to perhaps 20 % of the weight. And during normal
operation – even for running at high speeds – the force
becomes much lower. This means wheels can be used at high speeds, 200
km/h and more. Weak forces also means less vibrations, so that
compact steel-reinforced rubber may be used – for high
reliability.

Sled (bogie)
designs for such hybrid propulsion will be presented below –
for both beam types.

Beam Types

We may consider
two beam types: the traditional and the optimal.

The traditional
(most used) beam for suspended monorail is the hollow SIPEM beam, in
which bogies roll on wheels. Its width is approximately the same as
its height. This makes room for bogies running on two tracks, so that
traditional track switching can be used. But this beam width means
the beam can't be bent sideways for fine-tuning the track curvature
(nor twisted for starting and ending graded turns), so that this beam
type becomes unsuitable for building high-speed train lines. The
2C-beam to be described below solves this problem. The half-beams
making up the 2C-beam can also be transported in greater lengths and
be mounted in awkward terrain. As the two half-beam splices can be
located far apart, the assembled beam can be without weak parts.

The
2C-beam in cross-section

The
optimal beam has the track hanging under a truss plate or I-shaped
beam which is designed to withstand the weight of the train. (It is
actually the oldest type, having been used since 1901 in Wuppertal.)

The Hollow
Beam – with two Rails

We
are using a combination of wheels and air cushion for the optimal
compromise:
We are aiming for quite high speeds, but not so high speeds that
propulsion (linear
motors) must be provided by the track. This means the train line
will be as cheep and simple as when plain old-fashoned wheel bogies
are used. Wheels are used for pulling (and regeneratively braking)
the train, but only to the extent wheel forces are needed. Air
cushions lift as much weight as possible, but are controlled to stop
lifting before wheel traction is lost. At low speeds, air cushions
are unimportant and may be dispensed with. (In case of e.g.
compressor failure, the train could still roll along at well beyond
100 km/h, with only moderately annoying delays and mechanical wears.)

As
the speed increases, the forces to be excerted by wheels are
decreased, so the load carried by wheels may be reduced by perhaps 80
%. (Emergency braking is not done with wheels, but by clamping the
beam.) As the air cushions take care of the side forces, the forces
acting on the wheels are greatly reduced, so speeds a little above
200 km/h may be achievable. When movement is controlled with wheels,
the speed can be accurately controlled while stopping in a hill or in
strong winds.

Simple
air-surfing vanes could be used instead of compressor-generated air
cushions, but investing in air cushion equipment for the bogies gives
some extra advantages:

The
air cushion action can be accurately controlled.

Low-pressure
air cushion pads can be used under the beam.

Pressures
in the upper and lower air cushions can be rapidly reversed for
resisting wind swing.

Damaged
wheels can be assisted by air cushions – also at low speeds.

Air
cushion use can be increased for passing gaps – like in
switches and crossings.

Proactive
Suspensioncontrol
can be performed by a pneumatic lifter between the bogie and the
suspension rods.

Various
kinds of these wheel types may be used

The
flanged type to the left will not be interesting, as air cushions
acting on the side walls will ensure proper tracking.

The
steel wheel in the middle is simple and reliable. It shouldn't be too
noisy when most of the forces against the beam are eliminated by air
cushion operation. It has the advantage of being thin, giving low air
resistance at high speeds.

The
special rubber wheel to the right gives higher friction, so more of
the train weight can be air cushion carried before the pulling power
of the wheels becomes too low. If the rubber part of this wheel is
destroyed, the wheel should be able to function well as a steel wheel
– at least if the air cushion assistance is automatically
increased. Well armored compact rubber should work well here.

The
above picture doesn't show how the hub motor occupies most of the
wheel, but this is shown in the next picture. The hub motor will in
fact be a very thick stationary axle for the wheel, so there is no
need for an axle connecting two wheels running side-by-side. This
means the bogie can easily adapt to half-beam separation variations.

The
suspension.The part inside the train is approximately as shown in
the first picture in the chapter A
Universal Bogie: The suspension can move sideways (passively or
actively) by means of minibogies rolling along roof rails which
follow the curvature of the train roof. But in this design variation
the entire suspension control mechanism (except the motors in the
minibogies) is moved up to a nacelle above the train.(The gaps
above and below the nacelle should be minimized, so that the train
can still be quite close to the beam, keeping tunnel diameters <4
m.)

This
design variation doesn't use a centralized compressor, but has one
compressor in each suspension. As the compressed air has to run only
a short distance, it will lose little of its heat on the way. This
gives energy efficiency as well as little or no problems with
freezing at the air cushion pads. (Adiabatic operation)

The
bogie, its suspension and compressor hang together as one unit which
can easily be detached from the wagon below – because only
simple suspension rods (each with a power or signal cable attached)
go down to the wagon. (The contents of the nacelle could have been
placed in the bogie in the beam, but this would have caused a much
stronger air resistance.)

The
small distance between the roof rails means that the lifting force
from them can continue along one (carbon fiber) strap running around
the wagon between windows. It is also easier to protect the train
interior against precipitation etc. when there is a narrow slit in
the roof.

The
minibogies in the top of the wagon should be about half a meter long,
and have notches under each end. Horizontal crossbars on the lower
end of the two suspension rods are held in these notches. (One notch
should be slightly displaceable – to correct for geometric
inaccuracies when the minibogies go down the steeper part of the roof
rails. ±80 cm displacement should be allowed.)

The
picture seems to have one suspension rod going up to a piston in a
cylinder marked Lifter. This picture part should be regarded as
containing two superimposed suspension rods going up to two lifter
cylinders. (A signal cable runs along one of these rods, and a power
cable along the other.) Above these cylinders, the upper suspension
rods are attached in-line at the central part of the nacelle. These
are depicted in two colors for distinguishing those going to the left
and right side of the bogie. The short ones go to the air cushion
pads working against the bottom of the beam. (These pads should be
double, so that the nacelle can be positioned up between them and
close to the beam.) The four upper suspension rods are hollow (or
supplemented with tubes) for transferring air to or from the air
cushion pads. Three such rods/tubes may be needed for each bogie side
– in case separate air cushions are needed against the side
walls of a half-beams. Alternatively, sensors in the air cushion pads
can monitor the distance to the side walls, and local valves can
direct more air to the side where the wall is too close.

The
upper suspension rods should be fixed in relation to the nacelle, so
that train tilting is handled by only the lower part of the
suspension. But there should be a little flexibility up here, so that
these rods can adapt to some variation in the separation between the
half-beams.

The
mechanism in the nacelle is as follows: The compressor creates a high
air pressure in the pressure tank, from which computer-controlled
valves let air act in the lower or higher part of the system. Lifting
or tilting the wagon is done by increasing the air pressure under the
pistons in the lifter cylinders, and all the suspensions should
co-operate in doing this in the same manner. If done equally for both
cylinders, the wagon is simply lifted. If done differently for the
left and right cylinders, the wagon is tilted. The train may be left
to get its natural tilt, as determined by the gravity and the
centrifugal forces, and this is what the passengers will feel is
correct. This can be done by connecting the lower parts of the
cylinders with a shunt tube which equalizes the pressures. There
should be an adjustable valve in this tube – for controlling
the air resistance in the shunt, so that penduling is sufficiently
damped.

Air
from the compressor is also sent up to the upper air cushion pads
(three on each side), and the lower air cushion pads (one (split
fore-aft) on each side) may be connected to the air intake of the
compressor. A valve should be able to rapidly exchange these two
airflows if a tilting force is threatening with lifting up the wheels
on one side.

The
two lower suspension rods can be rotated when they are being attached
to or disconnected from a wagon, as they hang under pistons which can
be rotated in circular cylinders. A wagon (or train) to be attached,
is lifted by a bottom support so that the horizontal crossbars of all
the (properly aligned) low suspension rods are swallowed by roof
slits. A maintenance mechanic then goes along the roof and turns each
suspension rod 90°, ensuring each crossbar is being attached to a
minibogie in the roof. A single bogie and its suspension unit may be
exchanged on a wagon hanging under a special (open) service beam.

Each
wheel in the beam contains a hub motor, which (as shown by the inner
circles in wheels in the picture) occupies most of the wheel volume.
Such a motor (perhaps a Protean
motor) may develop 55
hp. That makes 220 hp for one bogie, or 1320 hp for a 6-bogie
front wagon. (This is a 28 meter long minimal train with a rear
elevator. A short or long wagon may be added, but as this will bring
along correspondingly more motors, we can check the power requirement
by considering the single wagon train.)

If
such a train, weighing perhaps 20 tons, were to negotiate a 10 % hill
at 200 km/h, it would be ascending at 5.56 m/s, needing 20000x5.56/75
= 1482 hp for just lifting the train. Most of the rolling resistance
will be removed by the air cushions created by means of additional
motors, but the air resistance remains to be overcome. The air
resistance at 200 km/h would require about 1000 hp. This is the air
resistance for an ordinary train. The beamway train has a
considerable additional air resistance from the bogies in that narrow
beam. On the other hand, it hasn't that air resisting underside, and
the air can be displaced to four sides instead of three. We might
guess if these differences cancel out.

1320-1000=320
hp remain for hill-climbing + the (strongly reduced) rolling
resistance. This means an ascension of only a few percent can be
managed at 200 km/h. At 100 km/h, the air resistance takes 250 hp and
getting up the 10 % hill takes 741 hp, leaving perhaps 300 hp for
acceleration. The 10 % hill can be managed in up to about 120 km/h.
If we don't like such a slowdown in hills, there are several
solutions:

Get
some propulsion from the compressor by letting the two rear air
cushion units open up their rear walls.

Run
with a wagon attached. A 24 meter rear wagon with five bogies adds
motor power about as much as it adds weight, but doesn't add much to
the air resistance.

Make
the train narrower, with passengers sitting 2+1 abreast. This
decreases both the weight and air resistance, but not bogie power.

Use
a miniloc in front of the train.

Or we could simply
reduce the distance between the suspensions, and have 10 microlocs
instead of 6. This will give suspension redundancy: If one
suspension fails, it is easier for the neighbors to provide the extra
lift. (There should be 2 m between the two first suspensions, and
between the two last. There would then be about 2.5-3 m gaps between
the central suspensions, for which suspension failure is less
problematic.) The train will now provide 2200 hp and have close to
1200 hp for hill-climbing. This is 81 % of the 1482 hp called for
above (for negotiating a 10 % hill at 200 km/h), so we could manage
an 8.1 % hill at 200 km/h. With 12 microlocs: 2640 hp, and 1640 hp
for hill-climbing. Sufficient, even though the many microlocs
increase the air resistance. (The 6-bogie example above should
perhaps rather be: 12 half-bogies, each using only the right or left
half-beam.)

As the miniloc is
needed only above 120 km/h, it is unusually easy to use. This is
because the higher the speed is, the lower is the pulling force
needed for supplying a certain number of horsepowers. Low pulling
force means we needn't worry about using a loc having a small
fraction of the train's weight. A miniloc with e.g. 2000 hp should
weight just a few tons, and if it hangs under eight wheels, the
wheel-protecting air cushion needn't steal much traction, ensuring
weight is put on the wheels only when really needed for traction.

Another variety of
this drive: Let each bogie have wheels on only one side. Odd-numbered
bogies have wheels on one side, and even-numbered bogies have wheels
on the other side. This will decrease the total air resistance in the
beam. Using different suspension side shift for left and right side
bogies, will give good control over penduling. The suspension
separation should now be much smaller, and then the wagons will be
more compatible with the low-separation wagons recommended in the
next chapter.

The
2C-beam may hang like this in an I-beam or truss (described
below).The 2C-beam can be much thinner and lighter now when it
needn't function as a beam.

The
optimal shape for a beam which has predominantly vertical loading,
is, as is well known by structural engineers: the I-beam,
which is tall, narrow and with right-left symmetry. In its most
efficient form it has flanges at the top and bottom. Another
improvement (when low weight is important) is to use a truss
structure. This can be widened out from a planar structure to a space
frame structure to the extent sideways-acting forces are expected.

This
S-shaped beam functions structurally as a flanged I-beam.As it is
made of steel, it could also be given the track for air cushion
operation.This beam is unsuitable for vertical wheels, as they
need too much space.

If
the beam and the rail are produced separately, it is possible to
choose between many different types of beam and rail. The size may
range from the really small one which enables a beamway to use a car
tunnel together with cars, and up to a large truss for long bridge
spans.

Other
materials than steel may be used for the beam. If the price is more
important than compactness, reinforced concrete may be used, and this
can usually be produced locally in suitable shapes, including more
efficient truss structures. An important advantage of the truss
structure is that wind can pass through the plate instead of
destroying the beamway. But the lower part of the plate, upon which
wheels run, should be compact and smooth.

If
the beam is molded, it is easy to make its ends suitable for direct
interconnection, and to imbed diagonal carbon wires whose tension may
be varied.

The
rail will, of course, not have its splices near the I-beam splices,
and this will greatly increase the total beam strength and
reliability.

Carbon
is a very interesting material for beamway trusses, especially if
nanotube structures can be produced. Future beamway truss production
may be like this: Captured CO2
is used as raw material in an "inverted combustion"
process. In a 3D plotter, carbon is deposited as nanotubes in a truss
pattern, controlled by electromagnetic fields. Where compression
resistance is needed, strong crystals are grown. (Bones get their
strength by growing hydroxyapatite crystals where compression
resistance is needed, and medieval bow makers used bone on the back,
compressed, side of the bows.)

This
I-beam of reinforced concrete is combined with a steel track
beam.Horizontal wheels with hub motors are used for propulsion,
but not for carrying weight.

Only
the lower part of this I-beam needs to be unblocked for train
passages, so the two adjacent I-beams of a double track line can
strengthen each other considerably with cross braces.

A
double version, with two gutters opening towards the middle, (and a
common power line,) will be useful for gauntlet
stretches (bridge spans and tunnels) and bidirectional single track
lines.

A
beamway line with little traffic could have a single track if the
trains were converted for reversed gutter in each line end loop: At a
gap in the line, each microloc is rotated 180°. (The lifter
cylinder rotates, but not the piston in it.) Cables down to the wagon
could be continuous if the two line ends rotate the microlocs in
different directions.

The
air cushion unit in this design may be something like 120 cm long: a
50 cm long air cushion unit on each end of the air cushion axle (in
the center of the gutter), and a bare 20 cm axle length in the
middle, on which two mechanical subsystems (both only vaguely
outlined here) grip:

The
suspension (red outline) is attached to the top of the lifter
cylinder, which enables active suspension. The piston in this
cylinder carries this microloc's part of the train weight. A
compressor (not shown) sends high-pressure air in under the piston –
for contributing to lifting the train in a controlled manner. The
compressor (which may be encased in a nacelle together with with the
cylinder) also delivers air to the air cushion unit, so that this
can slide through the gutter (the track). The suspension is firmly
attached to the air cushion unit, so if the train swings to one
side, the air cushion unit rotates with it in the circular profiled
gutter and gives its air pressure force in the right direction.

The
propulsion subsystem (green outline) is held up by the air cushion
unit axle, but is held with its wheels orthogonally to the I-beam.

Stopping
train pendulation is now very simple: Establish a mechanical
connection between the penduling suspension and the stable propulsion
subsystem. As they both meet at the air cushion unit axle, a friction
clutch (or a non-friction equivalent) should there give a suitably
strong connection between the two subsystems. The microloc's
controlling microprocessor should monitor pendulation and provide
some clutch connection each time the pendule movement approaches the
equilibrium position. Or a pneumatic (or hydraulic) damper could
continuously provide a damping mechanical connection.

Two
horizontal wheels (with hub motors) are visible in the cross-section
picture, but there may be two wheels on each side (superimposed in
the picture). The wheel(s) on the right side can be moved down and
away by means of the diaginal sliding mechanism indicated – or
perhaps rather swung down with a set of parallell arms. The microloc
(or the wagon, or the train) can then be lifted off the beam towards
the left side. A microloc can be exchanged by a service vehicle on
the adjacent track.

Having
horizontal wheels, not carrying any weight, is unconventional. But
these wheels are spared from orthogonal forces (along their axes) as
well as forces from debris in their track, so they can run very fast.
250 km/h shouldn't be too hard to achieve. A contributing factor here
is that the wheel diameter isn't limited by the space in the beam. If
Protean hub motors are
used, it should be more economical to use the standard version for
cars rather than ordering a special train version. This model maxes
out at 1300
rpm, corresponding to a wheel diameter of 82 cm for 200 km/h, or
102 cm for 250 km/h.

The
wheels have three functions: Propulsion (with regenerative braking),
stabilization and derail prevention.

Compact,
steel-reinforced rubber should work fine on these wheels. This gives
good traction, as well as quite little maintenance work. These wheels
(and the whole propulsion subsystem) can be really light-weight. If
some of this should fall apart, it has small consequences for the
train operation.

A
miniloc with some of these microlocs can have good pulling power even
if it is light. This is because its maximal traction doesn't depend
upon its weight, but upon how hard it can squeeze the wheels
together.

Crossing
in the same plane should be quite simple for I-beam based lines, as
the train only passes the lower part, so most of the two beams –
the upper parts – can meet in a solid X. The low I-beam can
simply be missing; the horizontal wheels on a fraction of the train
can do without this surface. The gutter can have short breaks for
passing trains, as the sled (air cushion unit) will be long, almost 2
meters long, and should be able to cross a half as wide gap. (The
mechanisms at gutter level, with green outline in the picture, could
be made quite narrow and close to the gutter.)

Track
switching can be done with movable
beams, as is common for monorails, and this method is well suited
for high-speed trains.

Air
Cushion Microlocs: Independent and Co-operating

Some
principles are common to the 2C-beam and I-beam varieties of air
cushion hovering: The microlocs should be independent and
co-operating, and the air cushion process should be adiabatic.

According
to the microloc philosophy, each microloc should have full
capabilities for hovering and propulsion. A central compressor may
seem more economical, but this would make the air cushion process
non-adiabatic.

Having
this process adiabatic, means: The heat which is generated during
compression is not allowed to escape, but it causes the air expansion
in the air cushion to give more lifting power than if the temperature
had decreased. Avoiding cooling is especially important in a cold and
moist environment, where additional cooling would give problems with
freezing where the air expands.

Adiabatic
operation implies: short distances and short storage times for the
compressed air – hence independently operating compressors in
the microlocs.

But
some redundancy is needed. A train shouldn't be disabled if one
microloc's compressor fails. The suspension separation should be so
small (e.g. 2 m) that adjacent suspensions (microlocs) can handle the
extra weight. When compression fails, the piston in the suspension
cylinder falls to the bottom, so this suspension stops lifting the
train, and only the weight of the microloc needs to be supported.
Small wheels at the ends of the air cushion pads can do this at low
speeds. The air cushion pads might have vanes for passive air cushion
hovering at higher speeds. But this means that trains using such
microlocs can run backwards only at low speeds. Some microloc
autonomy should be sacrificed, so that the microlocs to some extent
can share compressed air. The simplest way to do this is: Make the
air cushion units so long that they almost meet each other. Their
ends should be telescopic, so that when there is high air pressure,
the ends are pressed out, meeting and connecting with the neighbor,
so that compressed air can be shared. This would probably not give
sufficient lift for lifting the train, but at least the microloc can
lift itself.

In
case of total power loss, and vanes for passive hovering are unable
to ensure hovering down to steel roller speed: The power cables for
supplying power to the wagon are used for sending power from backup
batteries in the wagon. This power is used for running the air
compressors. Or power for the compressors is delivered by the hub
motors during regenerative braking. The train will then slow down in
a proper manner.

Passive
hovering and compressor-driving regenerative braking are now two
similar methods for converting kinetic energy into lift. If the vanes
for hovering are inconvenient or inefficient, they may now be
dispensed with.

Conclusion

The
I-beam design seems to be the best one, due to its flexibility and
simplicity.

Changes:

September
21. 2010: New article

September
27. 2010: New chapter: Air
Cushion Microlocs: Independent and Co-operating

October
3. 2010: The chapter Air
Cushion Microlocs: Independent and Co-operating is
extended with power-loss info.

December
1. 2010: The power computation is extended with 10 and 12 microloc
examples.